Q: Does the WinRT-based Remote Desktop client support RemoteFX?

A: Yes. The WinRT-based remote desktop client available in the Windows Store has full support for RemoteFX. It offers the same graphical fidelity as if you were connecting from the desktop remote desktop client.

The only feature of RemoteFX that isn't available from the WinRT remote desktop client is USB redirection, because of the sandbox WinRT applications run in.